(1) Field of the Invention
The present invention relates to a polymethacrylimide resin composition having an excellent impact resistance and heat resistance. More particularly, the present invention relates to a polymethacrylimide resin composition comprising a polymethacrylimide resin and a specific organosiloxane type graft copolymer.
(2) Description of the Related Art
A polymethacrylimide resin has an excellent heat resistance, transparency, and rigidity and is expected to be used as a new engineering plastic material, but the use of this resin is restricted because of a poor impact resistance thereof.
As a means for improving the impact resistance of a polymethacrylimide resin, a process in which a polybutadiene type graft rubber is incorporated in the polymethacrylimide resin is disclosed in Japanese Unexamined Patent Publication No. 52-63,989, but in this process, since unsaturated bonds remain in the polybutadiene type graft rubber, the resin composition is thermally unstable and a valuable resin composition having an excellent heat stability cannot be obtained in practice.
Furthermore, a process in which the processability and impact resistance of a polymethacrylimide resin are improved by incorporating a polyolefin such as an ethylene/propylene copolymer into the polymethacrylimide resin is disclosed in Japanese Examined Patent Publication No. 59-42,017. In this process, to obtain a good impact strength and melt flowability, a polymer of a specific vinyl monomer must be added as the third component, and the inherent heat resistance of the polymethacrylimide resin is sacrificed.